1. Field of Invention
The present invention relates in general to rechargeable batteries and method of producing same, and more particularly to rechargeable lithium ion batteries and method of producing same. More specifically, the present invention is concerned with a multilayer battery cell used as an essential element of the battery and a method of producing same.
2. Description of Prior Art
In order to clarify the task of the present invention, one known multilayer battery cell will be briefly described with reference to FIG. 11 of the accompanying drawings.
The drawing shows an enlarged sectional view of the known multilayer battery cell 9 for the battery. As shown, the known battery cell 9 comprises positive and negative electrode parts xe2x80x9cPxe2x80x9d and xe2x80x9cNxe2x80x9d which are put on each other to form a laminated assembly. The positive electrode part xe2x80x9cPxe2x80x9d comprises a metallic foil current collector 1 that has positive electrode layers 2 at both surfaces thereof and two separator films 3 and 4 that intimately put therebetween the positive electrode layers 2. Similar to this, the negative electrode part xe2x80x9cNxe2x80x9d comprises a metallic foil current collector 5 that has negative electrode layers 6 at both surfaces thereof and two separator films 7 and 8 that intimately put therebetween negative electrode layers 6. Although not shown, the multilayer battery cell 9 is to be wound up to form a shaped unit. The shaped unit is received in a case filled with an electrolytic solution. A lid is fixed to the case to complete the battery. This type battery is shown in page 542 of xe2x80x9cBattery Handbookxe2x80x9d issued from MARUZEN Co., Ltd. in 1995, and pages 217 and 320 of xe2x80x9cHigh Density Lithium Secondary Batteryxe2x80x9d issued from TECHNOSYSTEM Co., Ltd.
However, as is easily understood from the drawing, the multilayer battery cell 9 has a complicated structure due to usage of numerous parts and elements such as foil current collectors 1 and 5, and separator films 3, 4, 7 and 8. The complicated structure brings about not only a bulky construction of the battery but also a time-consuming production process of the same, that causes increase in cost of the battery.
It is therefore an object of the present invention to provide a multilayer battery cell which is simple in construction and easy to be produced.
According to a first aspect of the present invention, there is provided a multilayer battery cell comprising a separator film that is ion-conductive; a positive electrode layer disposed on one surface of the separator film, the positive electrode layer being provided by spraying on the surface of the separator film a first predetermined composition; a negative electrode layer disposed on the other surface of the separator film, the negative electrode layer being provided by applying on the other surface of the separator film a second predetermined composition; a first conductive layer disposed on the positive electrode layer and electrically connected to the same; and a second conductive layer disposed on the negative electrode layer and electrically connected to the same.
According to a second embodiment of the present invention, there is provided a multilayer battery cell which comprises an ion-conductive separator film including a porous plastic film that has pores filled with ion-conductive additive; a positive electrode layer disposed on one surface of the separator film, the positive electrode layer being provided by applying on the surface of the separator film an oxide of lithium metal complex; a negative electrode layer disposed on the other surface of the separator film, the negative electrode layer being provided by applying on the other surface of the separator film a carbon powder or an oxide of lithium metal complex; a first conducive layer disposed on the positive electrode layer and electrically connected to the same, the first conductive layer having a first portion that is in contact with both the separator film and the positive electrode layer; a second conductive layer disposed on the negative electrode layer and electrically connected to the same, the second conductive layer having a second portion that is in contact with both the separator film and the negative electrode layer; a first insulating layer disposed on the first conductive layer and having a portion that is in contact with both the separator film and the positive electrode layer; and a second insulating layer disposed on the second conductive layer and having a portion that is in contact with both the separator film and the negative electrode layer, wherein the positive and negative electrode layers, the first and second conductive layers and the first and second insulating layers are each provided by a spraying or printing process and wherein upon charging and discharging, ion transfer takes place between the positive and negative electrode layers through the separator film.
According to a third aspect of the present invention, there is provided a method of producing a multilayer battery. The method comprises conveying an ion-conductive separator film in a given direction, the separator film having first and second surfaces; spraying first and second predetermined compositions on the first and second surfaces of the separator film respectively, the first and second predetermined compositions being those for producing positive and negative electrode layers; drying the first and second predetermined compositions thereby to form the positive and negative electrode layers on the first and second surfaces of the separator film; spraying third and fourth predetermined compositions on the positive and negative electrode layers thus produced; and drying the third and fourth predetermined compositions thereby to form first and second conductive layers on the positive and negative electrode layers respectively.